diff --git a/eslint.config.mjs b/eslint.config.mjs
index 55b2459c..4042d38b 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -76,5 +76,42 @@ export default tseslint.config(
         ...globals.vitest,
       },
     },
+  },
+  {
+    // B2 Phase 1 step 5/5 — block new raw status-writes on tasks.
+    //
+    // During dual-write every `UPDATE tasks SET status = ...` must go
+    // through `advanceTaskPhase` (or the four grandfathered sites in
+    // database-base.ts / database/tasks-*.ts / database/runs.ts that
+    // already dual-write and carry `eslint-disable-next-line
+    // no-restricted-syntax` with a comment explaining the exemption).
+    // The no-restricted-syntax rule below intercepts string literals
+    // and template literals whose text starts with the offending SQL
+    // prefix. New code that needs to mutate `tasks.status` must either
+    // route through `advanceTaskPhase` (preferred) or add an
+    // `eslint-disable-next-line` with a rationale comment.
+    //
+    // Migrations are deliberately excluded — schema changes operate on
+    // the legacy column by design.
+    files: ["src/main/**/*.ts"],
+    ignores: ["src/main/database/migrations/**/*.ts"],
+    rules: {
+      "no-restricted-syntax": [
+        "error",
+        {
+          // Plain string literals and normal template heads.
+          selector:
+            "Literal[value=/\\b[Uu][Pp][Dd][Aa][Tt][Ee]\\s+tasks\\s+[Ss][Ee][Tt]\\s+status\\b/]",
+          message:
+            "B2 Phase 1: write task.status through advanceTaskPhase (or tag with `// eslint-disable-next-line no-restricted-syntax` + dual-write rationale for grandfathered sites).",
+        },
+        {
+          selector:
+            "TemplateElement[value.raw=/\\b[Uu][Pp][Dd][Aa][Tt][Ee]\\s+tasks\\s+[Ss][Ee][Tt]\\s+status\\b/]",
+          message:
+            "B2 Phase 1: write task.status through advanceTaskPhase (or tag with `// eslint-disable-next-line no-restricted-syntax` + dual-write rationale for grandfathered sites).",
+        },
+      ],
+    },
   }
 );
diff --git a/src/main/database-base.ts b/src/main/database-base.ts
index 54b7750e..77e625a9 100644
--- a/src/main/database-base.ts
+++ b/src/main/database-base.ts
@@ -422,6 +422,7 @@ export class AppDatabaseBase {
       interruptedCount = Number(result.changes);
       if (interruptedCount > 0) {
         this.db.prepare(
+          // eslint-disable-next-line no-restricted-syntax -- B2 Phase 1 grandfathered: crash-recovery sweep; trigger mirrors status→phase, step 3/5 already drops shadow leases below
           `update tasks set status = 'blocked', updated_at = ? where id in (select task_id from runs where status = 'interrupted' and finished_at = ?) and status in ('in_progress', 'todo')`,
         ).run(ts, ts);
       }
diff --git a/src/main/database/runs.ts b/src/main/database/runs.ts
index 5cebcc1d..c8a9c60b 100644
--- a/src/main/database/runs.ts
+++ b/src/main/database/runs.ts
@@ -161,6 +161,7 @@ export function buildRunMethods(
             // NOT EXISTS clause is the canonical "no live owner" check.
             getDb()
               .prepare(
+                // eslint-disable-next-line no-restricted-syntax -- B2 Phase 1 grandfathered: finishRun's "runNeverStarted" rollback; trigger mirrors status→phase, shadow lease already dropped above
                 `UPDATE tasks
                  SET status = 'todo',
                      checkout_run_id = NULL,
diff --git a/src/main/database/tasks-status.ts b/src/main/database/tasks-status.ts
index 7a896836..7ba9e7c3 100644
--- a/src/main/database/tasks-status.ts
+++ b/src/main/database/tasks-status.ts
@@ -377,6 +377,7 @@ export function buildTaskStatusMethods(
     ): void {
       const ts = nowIso();
       getDb()
+        // eslint-disable-next-line no-restricted-syntax -- B2 Phase 1 grandfathered: crash-recovery retry bounces task back to todo; trigger mirrors status→phase, no lease held at this point
         .prepare("update tasks set status = 'todo', updated_at = ? where id = ?")
         .run(ts, taskId);
       getDb()
@@ -402,6 +403,7 @@ export function buildTaskStatusMethods(
     markInterruptedTaskFailed(taskId: string): void {
       const ts = nowIso();
       getDb()
+        // eslint-disable-next-line no-restricted-syntax -- B2 Phase 1 grandfathered: crash-recovery terminal transition; trigger mirrors status→phase, lease was already cleared by interruptStaleRuns
         .prepare("update tasks set status = 'cancelled', updated_at = ? where id = ?")
         .run(ts, taskId);
     },